A hybrid vehicle may enter a regeneration mode from time to time. In regeneration mode, the vehicle's kinetic energy may be converted to electrical energy and stored for use at a later time. The vehicle may enter regeneration mode when a driver reduces demand torque to slow the vehicle or to reduce the vehicle's propensity to accelerate. For example, a vehicle may enter a regeneration mode in response to the vehicle approaching a stop sign and the driver lifting off the accelerator pedal. The vehicle may decelerate at a predetermined level after entering regeneration mode. As the vehicle decelerates, its transmission may downshift from a higher gear to a lower gear as vehicle speed decreases to keep engine and/or motor speed within a desired range. However, if transmission clutches do not transfer a desired amount of torque during the downshift, the driver may notice an objectionable driveline torque disturbance. Further, the driveline torque disturbance may be exacerbated in drivelines that include a driveline disconnect clutch, which increases the driveline inertia. Therefore, it may be desirable to provide a system and method of transmission downshifting that improves downshifting in a regeneration mode.
The inventors herein have recognized the above-mentioned issues and have developed a driveline operating method, comprising: adjusting torque applied to a transmission input shaft via a closed loop in response to a percentage of a transmission gear shift complete.
By adjusting motor torque in response to a percentage of a transmission gear shift that is complete, it may be possible to provide the technical result of reducing driveline torque disturbances during gear shifting of a fixed step ratio transmission. In particular, the pressure above stroke it takes to squeeze a clutch is directly related to the torque transmitted by a gear clutch. However, a gear clutch actuator may not have sufficient bandwidth to shape clutch slippage during a downshift to reduce driveline torque disturbances. One the other hand, an electric machine operating in a regeneration mode may have a higher torque bandwidth that may be utilized to manipulate torque transmitted via the gear clutch during shifting via adjusting electric machine torque. Thus, driveline torque disturbances may be reduced when a driveline is operating in a regeneration mode via adjusting electric machine torque.
The present description may provide several advantages. Specifically, the approach may reduce driveline torque disturbances during transmission gear downshifting. Additionally, the approach may include closed loop control to further reduce driveline torque disturbances. Additionally, the approach may include adapting control parameters so that open loop torque control may be improved.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.